Fused salt electrolytic cells



Dec. 29, 1959 s. E. BERGH FUSED SALT ELECTROLYTIC CELLS 4 Sheets-Sheet 1Filed July 22. 1957 Jib IN VEN TOR.

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ver re. E. zbafl h AGE/V7 Dec. 29, 1959 s, E. BERGH 2,919,238 I FUSEIDSALT ELECTROLYTIC CELLS Filed July 22, 1957 4 Sheets-Sheet 4uvilllllllllllr G Nr FUSED ssr'r nrncrnotvrrc CELLS Sverre E. Eergh,Lewiston, N.Y., assignor to E. I. du Pont de Nemours and Company,Wilmington, Del., a corporation of Delaware Application July 22, 1957,Serial No. 673,492

4 Claims. (Cl. 204247) This invention relates generally to improvementsin constructing fused salt electrolysis cells and more particularlyconcerns the method of supporting the basic elements of the fused saltcell suitable for the electrolytic production of sodium.

In the production of sodium from a fused salt mixture in a cell of theDowns type (see U.S.P. 1,501,756, dated July 15, 1924) it is importantthat the anode, cathode and diaphragm are maintained in carefulpredetermined alignment with each other so as to insure efficientproduction and long cell life. in large commercial cells the alignmentof these parts is difficult to maintain during the life of the cell inlarge part because heretofore the weight of these parts was supporteddirectly on the cell shell. However, changes in temperature and otherfactors make it difficult to establish the proper alignment betweenanode, cathode and diaphragm at start-up when I the cell temperaturerises from room temperature to operating temperature and later duringthe, life of the cell when it is often necessary to change the diaphragmor to shake it to dislodge adherent solids. This difiiculty has been aproblem of the industry for over 30 years and has not been solvedsatisfactorily prior to the present invention.

It is accordingly an object of the present invention to provide meansfor maintaining the proper alignment of anode, cathode and diaphragmwith respect to each other during the life of the fused salt cell. It isanother object to support the anode, cathode and diaphragm assemblycombined with the product collectors independent of the cell shell. Itis a further object to provide means for readily reproducing theoriginal alignment of the diaphragm with respect to the anode and thecathode after each diaphragm change.

These and other objects of the invention are accomplished by supportingthe cell shell, the anode, the cathode, and the collector-diaphragmassembly each independently of the other and on support outside of andindependent of the cell or its parts thereby achieving freedom ofvariable distortion caused by temperature changes inherent in the oldarrangement whereby all the parts or elements were supported by the cellwall.

The drawing accompanying this specification will serve to illustrate apreferred method for supporting the significant cell parts independentlyof each other as well as a standard cell to show the state of the priorart whereby all the other cell parts are supported on the cell shell.

Figure 1 is a vertical cross section of'a fused salt sodium cell showingthe relationship between the cell parts and their support independent ofeach other.

Figure 2 is a horizontal section at AA of the cell of Figure 1.

Figure 3 is a schematic end view of the cell of Figure 1 from BB.

Figure 4 shows the cell support system of a prior art standard sodiumcell in vertical cross section.

The identifying numbers in the figures all correspond ice to the sameelements. The cell is housed in steel shell 1 lined with refractorybrick 2 which together constitute the cell wall. Centrally andvertically disposed anode3 enters the cell from the bottom whereelectrical contact with the external power source not shown ismtablished by way of metal box 4. The bottom of the cell around theanode is comprised of refractorycement block 5 on which the cell wall ispositioned. Cylindrical steel cathode 6 surrounds the anode and has twoarms 7 extending through the cell wall for contact withthe externalelectrical circuit not shown. Cylindrical metal Wire mesh diaphragm 8divides the space between the anode and the cathode into anolyte andcatholyte zones and is suspended from the product collector system insuch a way that no part is in contact with either electrode and is asnearly symmetrically centered as possible. The collector systemcomprises the annular sodium collector 9 with a collector or riser pipe10 through which the sodium produced by electrolysis is removed from thecell. The collector system also includes thechlorine collector or dome11 which collects and provides for the removal of the gaseous componentof the electrolytic process from the cell. The diaphragm together withthe product collectors and their sub-elements are herein referred to asthe collector-diaphragm assembly.

The cell parts are supported by four main support columns 12 which reston foundation lla. Support or beam members 14 tie in with supportcolumns 12 and provide the support for the anode by way of insulators l5and beams 16 which latter directly support metal box 4 in which anode 3is fixed. Beams l7 resting on insulators 18 support the cell wall andare in turn supported on beams 14.

Beam or support members 19 support the weight of the cathode 6 by way ofcathode arms 7. An insulator 20 is interposed between member 19 and arm'7. T0 steady the cathode arm so as to provide precise verticalalignment side supports 21 preferably insulators are provided. Theseside supports may be attached to braces 22 which in turn may be attachedto beam'19 and brace 23. Cathode arms 7 since they pass through the cellwall and since the cell wall and the cathode expand unequally must beprovided with flexible sealing means such as metal bellows or disks 24which are integrally fastened to the cathode arm and to a metal member25 of the wall. lators 2% as the cathode expands. The spacer blocks 26may be used during erection and are preferably removed prior tostart-up. Means, not shown, may be provided to equalize the travel ofthetwo opposed cathode arms as they move due to cathode expansionspecifically as'the temperature of the cell is raised when it is placedin operation at fused bath temperatures.

Vertical supports 27 resting 011 horizontal beams 19 takethe weight ofthe collector-diaphragm assembly by way of horizontal frame member 28directly attached to the collector-diaphragm assembly. Insulators 29 areinterposed between supports 27 and member 28. Brace members 30 betweenmain support column 12 and vertical supports 27 may be used to providestability. Means .such as pins 31 are provided to fix the alignment ofthe collector-diaphragm assembly with respect to the other elements ofthe cell such as the cathode and the anode. On removal of thecollector-diaphragm assembly from the cell during operation the originalalignment of the collector-diaphragm with respect to the rest of thecell is easily reestablished as it existed before the removal by placingthe pins 31 into their proper openings. The pin 31 may also be fastenedon the top of insulator 29 with corresponding hole in member 28 toengage the fixed pin on placing or replacing the collector-diaphragmassembly in the cell.

The cathode arms may slide on the insu- Other means than pins, such asproperly placed grooves or the like may be used in place of the pins,provided only that thereby the proper realignment will result onreplacing the collector-diaphragm assembly after removalfor repair orfor replacement of the diaphragm as is often required in operatingcells.

It will thus be apparent that by supporting the weight of the essentialcell elements independently of the cell or the cell wall that betteralignment of the cell parts, particularly of the cathode, the anode andthe diaphragm with respect to each other can be maintained both duringthe period when the cell is heated to operating temperature and thevarious parts expand according to their expansion characteristics asWell as easily reestablishing the proper realignment on changing thecollector-diaphragm assembly and replacing it while the cell is inoperation.

The cells of this invention may comprise one or more vertically disposedanodes, each with its companion opposed cathode, preferably so arrangedthat the cathode surrounds the anode. The cathode must have at least twopreferably opposed arms extending through the cell wall. The verticallyplaced anode may be circular, rectangular, hexagonal or any other shapeprovided only that thecorresponding cathode surface be disposed at auniform distance from the anode surface throughout the electrolyticzone. The distance between the electrolytic anode and cathode surfacesmust be uniform and should generally not exceed three inches and shouldpreferably be less than two inches.

While the four elements described above are independently supportedexternal to and independent of the cell body it is necessary that theybe insulated from each other to avoid electrical short-circuits.

This invention is generally applicable to electrolytic cells involvingthe electrolysis of fused salt mixtures where the metal product of theelectrolysis will float on the cell bath and both the anodic andcathodic products are collected at the top of the cell rather than atthe bottom. The invention more specifically applies to electrolyticcells for .the production of alkali metals, particularly sodium, fromfused salt mixture of the halides of the metals, preferably thechlorides but fluorides may also be present.

I claim:

1. In a cell for the electrolytic production of a metal having a densitybelow the density of the fused electrolyte and requiring a diaphragm toseparate the anode and cathode zones the combination comprising fourelements each supported on support external to the cell body, the firstelement comprising the cell shell, the second element comprising avertically disposed anode with bottom entrance into the cell, the thirdelement comprising a cathode surrounding the anode said cathode havingopposed arms, said arms passing through the cell wall and beingsupported on weight bearing means outside said cell wall and the fourthelement comprising collecting means for the metal and non-metal productsof the elec- 2. In a cell for the electrolytic production of a metal Ihaving a density below the density of the fused electrolyte andrequiring a diaphragm to separate the anode and cathode zones thecombination comprising four elements each supported on support externalto the cell body, the first element comprising the cell shell, thesecond element comprising a vertically disposed anode with bottomentrance into the cell, the third element comprising a cathodesurrounding the anode, said cathode having opposed arms, said armspassing through the cell wall and being supported on weight bearingmeans outside said cell wall and the fourth element comprisingcollecting means for the metal and non-metal products of theelectrolytic cell, a diaphragm suspended from said collecting means,said diaphragm being disposed between the anode and the cathode, saidfourth element being removable as a whole from said cell and thenreplaceable in means fixing the exact previous alignment of said fourthelement with the other cell elements.

3. In a cell for the production of alkali metal by the electrolysis of afused salt bath the combination comprising an anode vertically disposedin the cell, said anode entering the electrolyte from the bottom of saidcell, said anode being supported separately from the cell wall, acathode surrounding said anode so as to create an electrolysis zonebetween said anode and said cathode not exceeding a distance of about 2inches over the major portion of the opposed electrodes, said cathodehaving at least two opposed arms, said arms passing through the cellwall and said cathode and arms supported on Weight bearing memberoutside of and independent of said cell wall, and a collector-diaphragmassembly comprising an alkali metal collector, a chlorine gas collectorand a porous metal diaphragm, said diaphragm extending down- Ward intothe electrolysis zone between said anode and said cathode to createtherein anolyte and catholyte zones, said collector-diaphragm assemblybeing supported independently of said cell wall and of said anode and ofsaid cathode.

4. The cell of claim 3 further characterized in that the support forsaid collector-diaphragm assembly contains means for accuratelycentering said assembly so that said diaphragm will fit between saidanode and said cathode without contacting either of them, said meanspermitting the removal of said assembly and its replacement in thepredetermined alignment.

References Cited in the (hoof this patent .UNITED STATES PATENTS2,592,483 Smith et al. Apr. 8, 1952 FOREIGN PATENTS 104,955 Germany Aug.30, 1899

1. IN A CELL FOR THE ELECTROYTIC PRODUCTION OF A METAL HAVING A DENSITY BELOW THE DENSITY OF THE FUSED ELECTROLYTE AND REQUIRING A DIAPHRAGM TO SEPARATE THE ANODE AND CATHODE ZONES THE COMBINATION COMPRISING FOUR ELEMENTS EACH SUPPORTED ON SUPORT EXTERNAL TO THE CELL BODY, THE FIRST ELEMENT COMPRISING THE CELL SHELL, THE SECOND ELEMENT COMPRISING A VERTICALLY DISPOSED ANODE WITH BOTTOM ENTRANCE INTO THE CELL,THE THIRD ELEMENT COMPRISING A CATHODE SURROUNDING THE ANODE SAID CATHODE HAVING OPPOSED ARMS, SAID ARMS PASSING THROUGH THE CELL WALL AND BEING SUPPORTED ON WEIGHT BEARING MEANS OUTSIDE SAID CELL WALL AND THE FOURTH ELEMENT COMPRISING COLLECTING MEANS FOR THE METAL AND NON-METAL PRODUCTS OF THE ELECTROLYTIC CELL, A DISAPHRAGM SUSPENDED FROM SAID COLLECTING MEANS, SAID DIAPHRAGM BEING DISPOSED BETWEEN THE ANODE AND THE CATHODE, SAID FOURTH ELEMENT BEING REMOVABLE AS A WHOLE FROM SAID CELL. 